The basal ganglia (BG) show diverse functions for motor and cognition. Here, we are concerned about action selection performed by the BG. Particularly, we make quantitative analysis of roles of direct pathway (DP) and indirect pathway (IP) for action selection in a spiking neural network with 3 competing channels. For such quantitative work, in each channel, we get the competition degree C_d, given by the ratio of strength of DP (S_DP) to strength of IP (S_IP) (i.e., C_d = S_DP / S_IP). Then, desired action is selected in the channel with the largest C_d. Desired action selection is made mainly due to strong focused inhibitory projection to the output nucleus, SNr (substantia nigra pars reticulata) via the "Go" DP in the corresponding channel. Unlike the case of DP, there are two types of IPs; intra-channel IP and inter-channel IP, due to widespread diffusive excitation from the STN (subthalamic nucleus). The intra-channel "No-Go" IP plays a role of brake to suppress the desired action selection. On the other hand, the inter-channel IP to the SNr in the neighboring channels suppresses competing actions, leading to spotlight the desired action selection. In this way, role of the inter-channel IP is opposite to that of the intra-channel IP. But, to the best of our knowledge, no quantitative analysis for such roles of the DP and the two IPs was made. Here, by direct calculations of the DP and the intra- and the inter-channel IP presynaptic currents into the SNr in each channel, we get the competition degree of each channel to determine a desired action, and then roles of the DP and the intra- and inter-channel IPs are quantitatively made clear.

中文翻译：

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基底神经节直接和间接通路对动作选择的作用的定量分析

基底神经节 (BG) 显示出多种运动和认知功能。在这里，我们关心的是 BG 执行的操作选择。特别是，我们对直接通路 (DP) 和间接通路 (IP) 在具有 3 个竞争通道的尖峰神经网络中的动作选择中的作用进行了定量分析。对于这样的定量工作，在每个通道中，我们得到竞争度C _d，由DP强度( S _DP )与IP强度( S _IP )之比给出(即C _d = S _DP / S _IP )。然后，在具有最大C _{d 的}通道中选择期望的动作。所需的动作选择主要是由于通过相应通道中的“Go”DP 对输出核 SNr（黑质网状部）的强聚焦抑制投射而做出的。与 DP 的情况不同，IP 有两种类型：通道内 IP 和通道间 IP，归因于 STN（丘脑底核）的广泛扩散激发。通道内“No-Go”IP 起到制动作用，抑制所需的动作选择。另一方面，相邻通道中 SNr 的通道间 IP 抑制了竞争动作，从而突出了所需的动作选择。这样，通道间IP的作用与通道内IP的作用相反。但据我们所知，没有对DP和两个IP的角色进行定量分析。这里，通过直接计算进入每个通道的 SNr 的 DP 和通道内和通道间 IP 突触前电流，我们得到每个通道的竞争程度，以确定所需的动作，然后确定 DP 和通道内的角色。 ——渠道间IP量化明确。